The present invention is in a process for the production of 2-cyanoiminothiazolidine by reacting 2-aminoethanethiol (cysteamine) with a dialkyl-N-cyanoimidocarbonate.
The synthesis of 2-cyanoiminothiazolidine using 2-aminoethanethiol is known. Thus the German laid-open specification DE 22 05 745 describes new heterocyclics substituted by a N-cyanoimino residue and processes for their production and inter alia the reaction of 2-aminoethanethiol with dialkyl-N-cyanoimido-dithiocarbonates. However, this process has the serious disadvantage that mercaptans are released during the reaction in twice the stoichiometric amount which are extremely difficult and time-consuming to handle because of their toxicity and their foul odor.
R. L. Webb et al., in J. Heterocycl. Chem. 24, 275, 1987 describe the use of diphenyl-N-cyanoimidocarbonate to produce 2-cyanoiminothiazolidine. Since diphenyl-N-cyanoimidocarbonate is not available in large amounts as a starting compound and the complete separation of the phenol released during the reaction from the reaction product is very time consuming, this process is unsuitable for an industrial production of 2-cyanoiminothiazolidine.
The production of 2-cyanoiminothiazolidine by reacting 2-aminoethanethiol with dimethyl-N-cyanoimidocarbonate in aqueous solution was described by I. Zmitek et al., in Org. Prep. Proced. Ind. 23, 721, (1991). However, the long reaction time and the small yield of 48% obtained in this way, render this process uneconomical. In addition, the physical data presented therein raises doubts as to whether the isolated and described product really is 2-cyanoiminothiazolidine.